For many years, magnetic recording tape has been utilized as an inexpensive and reliable medium for the storage and retrieval of data processing information. In the personal computer industry, it has become the practice to use tape cartridges to hold the tape and facilitate easy loading of the magnetic tape into a suitably adapted tape drive. Moreover, cartridges protect the magnetic recording tape from contamination and inadvertent contact during operation within the tape drive, as well as during storage outside of the tape drive. Wide acceptance of tape cartridges promoted adoption of standard configurations by the data processing industry.
As the data processing industry advances, there is a need for larger-capacity, belt-driven tape cartridges. Such larger tape cartridges may have a cartridge-drive interface compatible with commercially available industry standard tape drives. If the cartridge is not compatible with industry standard tape drives, the cartridge should have a mechanism to prevent the cartridge from being inserted into an incompatible tape drive.
One way to increase the capacity of a tape cartridge is to increase the length of tape stored therein. Since the volume within a tape cartridge is limited, some cartridge designs increase tape length by decreasing the thickness of the tape. Other designs increase available volume by extending the length of the cartridge while maintaining an industry standard cartridge-drive interface (see, for example, U.S. Pat. No. 4,262,860).
However, lengthening the tape exacerbates undesirable characteristics in the cartridge design. For example, tape tension is attributable to the difference in belt tensions applied to the two tape packs. This is a function of the diameters of the two packs and changes as tape moves from one pack to the other. A bow-tie tension profile of tape moving within a conventional belt-driven tape cartridge indicates the change in tape tension over the entire length of tape as it moves from hub to hub within the cartridge. The bow-tie profile is partly determined by the ratio of the diameter of an empty hub to the diameter of a full tape pack on a hub. Since a longer tape results in an increased tape pack diameter, a longer tape worsens the bow-tie profile of tape tension for a given design of tape cartridge.
Similarly, the tangential drive force ("TDF") is the amount of force needed to drive the tape within a cartridge in either direction. TDF is determined by the total drag of all components in the cartridge and is preferably constant regardless of the amount of tape on each pack. The drags produced by certain components, like the rollers guiding the drive belt, however, vary as a function of the tape pack diameter. As with the bow-tie tension profile, therefore, a longer tape results in a greater variation in TDF as the tape moves from pack to pack. These variations in the bow-tie tension and TDF profiles may detract from the performance of the tape cartridge.
In addition, the tape in the tape packs tends to vertically shift when the tape cartridge is subject to stress. To limit the extent of this shift, some tape cartridges have flanges attached to the top and bottom of each hub. However, these flanges cannot withstand high levels of stress and are not adequate for large tape packs.
Industry standard tape cartridges, moreover, have a door pivotally mounted at the front of the cartridge to protect the tape media passing through an opening in the front face of the cartridge housing when the cartridge is outside of a tape drive. The door is typically biased closed when the cartridge is outside the drive, and cammed open by a rail in the tape drive when the cartridge is inserted therein. The door, however, does not cover a second opening in the front face through which the drive roller and portion of the tape are exposed, and which allows dust and other contaminates to contact the media.
Industry standard tape cartridges additionally have a write protect lock located near the front left corner of the cartridge. This lock is typically a sliding or rotating two-position switch and is often difficult to manipulate.
Accordingly, there is a need for an increased capacity cartridge having a mechanism for preventing insertion into a non-compatible drive and decreased variation in tape tension and TDF commonly associated with cartridges having increased tape length. In addition, the cartridge should have improved hubs to support the larger tape packs, a door that more efficiently protects the media from contamination, and a write protect lock that is easier to manipulate.